The tread belt pneumatic tires of the present invention are generally designed for use on large earthmover vehicles and are subjected to high stress and loads under harsh environmental conditions such as in rock quarries, mines, foundries, and other areas where tires are subjected to puncture-producing and wear-inducing conditions.
As discussed in U.S. Pat. No. 4,351,380, certain prior art tread belt tire assemblies comprise a plurality of ground-engaging shoes spaced about the periphery of the supporting structure. The heavy loads on the shoes result in great stresses being developed that sometimes lead to premature tire failure. The U.S. Pat. No. 4,351,380 is directed to an improved track belt assembly which comprise a plurality of shoes spaced about the periphery of a load-supporting structure and secured to a reinforcing belt structure disposed on the side of the shoe opposite the ground-engaging side thereof.
The large pneumatic tires, which are typically used for earthmoving vehicles, sometimes fail due to the high stress and loads caused by the harsh environmental conditions in which they are operated. These large prior art pneumatic tires had a greater tendency to fail in one of three tire locations or areas. The first problem area was that the turn-up end of the ply would sometimes break through the sidewall of the tire. A second problem area was a tire failure in the bead area. The third problem area was a tendency to fail in the crown and/or shoulder area of the tire.
In the prior art, conventional solutions to these problems include increasing the gauge of the sidewall to increase the bending stiffness, increasing bead area stiffness and robustness, and decreasing tire deformation under load by increasing the sidewall stiffness. To further improve tire durability, the ply turn-up portion of tires was typically reinforced.
In U.S. Pat. No. 4,609,023, having a common assignee with the present invention, the sidewall inserts were incorporated in the tire carcass to allow the ply structure to conform to its natural shape when the tire is inflated.
The most relevant prior art patent, U.S. Pat. No. 4,050,495, issued Sep. 27, 1977, teaches the use of a removable tread belt installed as an annular belt about the circumference of a tire carcass. The tread belt included laterally extending bars encapsulated in a matrix of rubber. The ends of the bars extended outwardly to a point beyond the widest portion of the carcass sidewall. The tread belt was rigidly supported by the bars at the ends of the tread belt to prevent deflection of the overhanging and otherwise unsupported tread belt at the lateral ends.
With the continual drive to improve earthmover performance, there is a continuing need to provide novel methods and tire designs for improving earthmover tire durability. The present invention is directed to an improved pneumatic tire and removable tread belt assembly with which the frequency of premature tire failure is thought to be substantially reduced. The present invention is also directed to providing an improved pneumatic tire and tread belt assembly which is designed to allow large tires to be transported in several sections and then assembled at the construction site to ease the otherwise difficult problem of transporting the large tires, i.e. sometimes over 13 feet in height and approximately 8,000 to 15,000 pounds. Moreover, the present invention relates to an improved pneumatic tire and removable tread belt assembly with which the driving characteristics of the tire can be more economically changed and the inventory of the number of tire spares that are typically needed can be reduced.
Objects and Summary of the Invention
It is an object of the present invention to provide a pneumatic tire for an earthmover vehicle, the pneumatic tire being as defined in one or more of the appended claims and, as such, having the capability of being constructed to accomplish one or more of the following subsidiary objects.
It is another object of the present invention to provide an improved tire and removable tread belt assembly for an earthmover vehicle wherein the frequency of premature tire failure has been substantially reduced.
Another object of the present invention is directed to providing an improved tire and removable tread belt assembly which is designed to allow large tires to be transported in several sections and then assembled at the delivery site.
Still another object of the present invention is to provide an improved tire and removable tread belt assembly with which the driving characteristics of the tire can be quickly and economically changed.
Yet another object of the present invention is to provide an improved tire and removable tread belt assembly with which the number of tire spares that are stored in inventory can be reduced.
Still another object of the present invention is to provide an improved tire and removable tread belt assembly with a unique tread belt that is restrained from expanding radially outwardly.
A further object of the present invention is to provide an improved tire and removable tread belt assembly wherein the tire treads will maintain a more flat tread profile which will improve tread life and durability.
A still further object of the present invention is to provide an improved tire and removable tread belt assembly wherein the belt is constructed to provide penetration protection.
In accordance with an embodiment of the invention a two-piece tire assembly is disclosed. The two-piece tire assembly has a removable tread belt for installing about the circumference of a tire carcass and a tire carcass having an inflated and unloaded outer circumferential surface having an axial dimension no greater than the axial width of the removable tread belt.
The tread belt has a pair of lateral ends each axially extending beyond the inflated unloaded carcass at the circumferential surface by a distance of at least 4% of carcass width as measured at the tread belt and carcass interface, and wherein the tread belt width is at least equal to or wider than the loaded deflected carcass width as measured at the outer circumferential surface of the carcass.
Each lateral end of the tread belt has a plurality of circumferentially extending substantially zero degree oriented cords in a first reinforcement layer and is radially inwardly flexible under load.
The tread belt preferably has a radially outer surface having a substantially flat tread arc radius R1 between the lateral ends extending from 50% to 75% of the tread belt axial width and a smaller tread arc radius R2 extending from each of the lateral ends to the first tread arc R1, the radially outer tread surface having a sloping surface extending from a tangency to R2 to a lateral end. The radial difference in the tread belt surface as measured at the centerline of the tread belt and each lateral end of the removable tread belt is greater than 0.3% of the outside diameter as measured at the centerline of the tread belt.
The tread belt has a belt reinforcing structure radially outward of the circumferentially extending cords in the first reinforcement layer. The belt reinforcing structure has a pair of cross-plies and a radially outer ply having cords oriented substantially 90 relative to the circumferentially extending cords in a first reinforcement layer.
Definitions
“Apex” means a non-reinforced elastomer positioned radially about a bead core.
“Aspect ratio” of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100% for expression as a percentage.
“Axial” and “axially” mean lines or directions that are parallel to the axis of rotation of the tire.
“Bead” means that part of the tire comprising an annular tensile member wrapped by the ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.
“Belt or breaker reinforcing structure” means at least two layers of plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17° to 75° with respect to the equatorial plane of the tire.
“Bias ply tire” means a tire having a carcass with reinforcing cords in the carcass ply extending diagonally across the tire from bead core to bead core at about 25–50 angle with respect to the equatorial plane of the tire. Cords run at opposite angles in alternate layers.
“Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.
“Chafers” refers to narrow strips of material placed around the outside of the bead to protect cord plies from degradation and chaffing caused by movement of the rim against the tire.
“Chippers” means a reinforcement structure located in the bead portion of the tire.
“Cord” means one of the reinforcement strands of which the plies in the tire are comprised.
“Equatorial plane (EP)” means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.
“Flipper” means a reinforced fabric wrapped about the bead core and apex.
“Footprint” means the contact patch or area of contact of the tire tread with a flat surface under load and pressure.
“Inner liner” means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating gas or fluid within the tire.
“Net-to-gross ratio” means the ratio of the tire tread rubber that makes contact with the road surface while in the footprint, divided by the area of the tread in the footprint, including non-contacting portions such as grooves.
“Nominal rim diameter” means the diameter of the rim base at the location where the bead of the tire seals.
“Normal inflation pressure” refers to the specific design inflation pressure at a specific load assigned by the appropriate standards organization for the service condition for the tire.
“Normal load” refers to the specific load at a specific design inflation pressure assigned by the appropriate standards organization for the service condition for the tire.
“Ply” means a continuous layer of rubber-coated parallel cords.
“Radial” and “radially” mean directions extending radially toward or away from the axis of rotation of the tire.
“Radial-ply tire” means a belted or circumferentially-restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65 and 90 with respect to the equatorial plane of the tire.
“Section height (SH)” means the radial distance from the nominal rim diameter to the outer diameter of the tire at its equatorial plane.